scriptless

Scriptless describes cryptographic approaches to implementing contract-like behavior without using traditional on-chain scripting. In blockchain discourse, scriptless methods rely on off-chain protocols and cryptographic signatures to enforce conditional outcomes, settling on-chain only when necessary. The term emphasizes avoiding bespoke on-chain scripts while preserving security and verifiability.

In Bitcoin, "Scriptless Scripts" is a well-known line of constructions introduced to enable smart-contract-like functionality without extending Bitcoin's Script language. Pioneered by Andrew Poelstra and collaborators, these techniques use adaptor signatures and related gadgets to encode conditions that would normally be encoded in a script, but are satisfied via off-chain interactions and only settled on-chain when required.

How it works: participants exchange signed messages that are valid only if a cryptographic condition holds. If the condition is satisfied, preimages or signatures can be revealed to claim funds; if not, the contract can be settled through standard on-chain transactions. This design mirrors certain scripted contracts while remaining scriptless on chain, and typically leverages Schnorr signatures and the Taproot upgrade.

Applications include cross-chain atomic swaps, off-chain payment channels, and escrow arrangements, where parties want complex agreement logic without bloating or complicating the on-chain scripting environment.

Benefits include reduced on-chain data, improved privacy, and compatibility with existing wallets that do not support new script primitives. Limitations involve reliance on specific cryptographic assumptions, added protocol complexity, and the need for broad wallet and node support to realize widespread use.

See also: Bitcoin Script, Taproot, Schnorr signatures, adaptor signatures, Lightning Network, off-chain contracts.